As the debate over health reform moves forward, you will hear a lot about the need for 60 votes in the Senate to pass reform due the threat of filibuster. Here is some background on filibuster and cloture (to cut off debate) from the historian of the Senate.
“Using the filibuster to delay or block legislative action has a long history. The term filibuster -- from a Dutch word meaning "pirate" -- became popular in the 1850s, when it was applied to efforts to hold the Senate floor in order to prevent a vote on a bill.
In the early years of Congress, representatives as well as senators could filibuster. As the House of Representatives grew in numbers, however, revisions to the House rules limited debate. In the smaller Senate, unlimited debate continued on the grounds that any senator should have the right to speak as long as necessary on any issue.
In 1841, when the Democratic minority hoped to block a bank bill promoted by Kentucky Senator Henry Clay, he threatened to change Senate rules to allow the majority to close debate. Missouri Senator Thomas Hart Benton rebuked Clay for trying to stifle the Senate's right to unlimited debate.
Three quarters of a century later, in 1917, senators adopted a rule (Rule 22), at the urging President Woodrow Wilson, that allowed the Senate to end a debate with a two-thirds majority vote, a device known as "cloture." The new Senate rule was first put to the test in 1919, when the Senate invoked cloture to end a filibuster against the Treaty of Versailles. Even with the new cloture rule, filibusters remained an effective means to block legislation, since a two-thirds vote is difficult to obtain. Over the next five decades, the Senate occasionally tried to invoke cloture, but usually failed to gain the necessary two-thirds vote. Filibusters were particularly useful to Southern senators who sought to block civil rights legislation, including anti-lynching legislation, until cloture was invoked after a fifty-seven day filibuster against the Civil Right Act of 1964. In 1975, the Senate reduced the number of votes required for cloture from two-thirds to three-fifths, or sixty of the current one hundred senators.
Many Americans are familiar with the filibuster conducted by Jimmy Stewart, playing Senator Jefferson Smith in Frank Capra's film Mr. Smith Goes to Washington, but there have been some famous filibusters in the real-life Senate as well. During the 1930s, Senator Huey P. Long effectively used the filibuster against bills that he thought favored the rich over the poor. The Louisiana senator frustrated his colleagues while entertaining spectators with his recitations of Shakespeare and his reading of recipes for "pot-likkers." Long once held the Senate floor for fifteen hours. The record for the longest individual speech goes to South Carolina's J. Strom Thurmond who filibustered for 24 hours and 18 minutes against the Civil Rights Act of 1957.”